1// Components for manipulating non-owning sequences of characters -*- C++ -*-
3// Copyright (C) 2013-2024 Free Software Foundation, Inc.
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
25/** @file include/string_view
26 * This is a Standard C++ Library header.
30// N3762 basic_string_view library
33#ifndef _GLIBCXX_STRING_VIEW
34#define _GLIBCXX_STRING_VIEW 1
37#pragma GCC system_header
40#define __glibcxx_want_constexpr_char_traits
41#define __glibcxx_want_constexpr_string_view
42#define __glibcxx_want_freestanding_string_view
43#define __glibcxx_want_string_view
44#define __glibcxx_want_starts_ends_with
45#define __glibcxx_want_string_contains
46#include <bits/version.h>
48#if __cplusplus >= 201703L
50#include <bits/char_traits.h>
51#include <bits/functexcept.h>
52#include <bits/functional_hash.h>
53#include <bits/range_access.h>
54#include <bits/stl_algobase.h>
55#include <ext/numeric_traits.h>
57#if __cplusplus >= 202002L
58# include <bits/ranges_base.h>
63# include <bits/ostream_insert.h>
66namespace std _GLIBCXX_VISIBILITY(default)
68_GLIBCXX_BEGIN_NAMESPACE_VERSION
70 // Helper for basic_string and basic_string_view members.
72 __sv_check(size_t __size, size_t __pos, const char* __s)
75 __throw_out_of_range_fmt(__N("%s: __pos (which is %zu) > __size "
76 "(which is %zu)"), __s, __pos, __size);
80 // Helper for basic_string members.
81 // NB: __sv_limit doesn't check for a bad __pos value.
83 __sv_limit(size_t __size, size_t __pos, size_t __off) noexcept
85 const bool __testoff = __off < __size - __pos;
86 return __testoff ? __off : __size - __pos;
90 * @class basic_string_view <string_view>
91 * @brief A non-owning reference to a string.
96 * @tparam _CharT Type of character
97 * @tparam _Traits Traits for character type, defaults to
98 * char_traits<_CharT>.
100 * A basic_string_view looks like this:
107 template<typename _CharT, typename _Traits = std::char_traits<_CharT>>
108 class basic_string_view
110 static_assert(!is_array_v<_CharT>);
111 static_assert(is_trivial_v<_CharT> && is_standard_layout_v<_CharT>);
112 static_assert(is_same_v<_CharT, typename _Traits::char_type>);
117 using traits_type = _Traits;
118 using value_type = _CharT;
119 using pointer = value_type*;
120 using const_pointer = const value_type*;
121 using reference = value_type&;
122 using const_reference = const value_type&;
123 using const_iterator = const value_type*;
124 using iterator = const_iterator;
125 using const_reverse_iterator = std::reverse_iterator<const_iterator>;
126 using reverse_iterator = const_reverse_iterator;
127 using size_type = size_t;
128 using difference_type = ptrdiff_t;
129 static constexpr size_type npos = size_type(-1);
131 // [string.view.cons], construction and assignment
134 basic_string_view() noexcept
135 : _M_len{0}, _M_str{nullptr}
138 constexpr basic_string_view(const basic_string_view&) noexcept = default;
140 [[__gnu__::__nonnull__]]
142 basic_string_view(const _CharT* __str) noexcept
143 : _M_len{traits_type::length(__str)},
148 basic_string_view(const _CharT* __str, size_type __len) noexcept
149 : _M_len{__len}, _M_str{__str}
152#if __cplusplus >= 202002L && __cpp_lib_concepts
153 template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
154 requires same_as<iter_value_t<_It>, _CharT>
155 && (!convertible_to<_End, size_type>)
157 basic_string_view(_It __first, _End __last)
158 noexcept(noexcept(__last - __first))
159 : _M_len(__last - __first), _M_str(std::to_address(__first))
162#if __cplusplus > 202002L
163 template<typename _Range, typename _DRange = remove_cvref_t<_Range>>
164 requires (!is_same_v<_DRange, basic_string_view>)
165 && ranges::contiguous_range<_Range>
166 && ranges::sized_range<_Range>
167 && is_same_v<ranges::range_value_t<_Range>, _CharT>
168 && (!is_convertible_v<_Range, const _CharT*>)
169 && (!requires (_DRange& __d) {
170 __d.operator ::std::basic_string_view<_CharT, _Traits>();
173 basic_string_view(_Range&& __r)
174 noexcept(noexcept(ranges::size(__r)) && noexcept(ranges::data(__r)))
175 : _M_len(ranges::size(__r)), _M_str(ranges::data(__r))
178 basic_string_view(nullptr_t) = delete;
182 constexpr basic_string_view&
183 operator=(const basic_string_view&) noexcept = default;
185 // [string.view.iterators], iterator support
188 constexpr const_iterator
189 begin() const noexcept
190 { return this->_M_str; }
193 constexpr const_iterator
195 { return this->_M_str + this->_M_len; }
198 constexpr const_iterator
199 cbegin() const noexcept
200 { return this->_M_str; }
203 constexpr const_iterator
204 cend() const noexcept
205 { return this->_M_str + this->_M_len; }
208 constexpr const_reverse_iterator
209 rbegin() const noexcept
210 { return const_reverse_iterator(this->end()); }
213 constexpr const_reverse_iterator
214 rend() const noexcept
215 { return const_reverse_iterator(this->begin()); }
218 constexpr const_reverse_iterator
219 crbegin() const noexcept
220 { return const_reverse_iterator(this->end()); }
223 constexpr const_reverse_iterator
224 crend() const noexcept
225 { return const_reverse_iterator(this->begin()); }
227 // [string.view.capacity], capacity
231 size() const noexcept
232 { return this->_M_len; }
236 length() const noexcept
241 max_size() const noexcept
243 return (npos - sizeof(size_type) - sizeof(void*))
244 / sizeof(value_type) / 4;
249 empty() const noexcept
250 { return this->_M_len == 0; }
252 // [string.view.access], element access
255 constexpr const_reference
256 operator[](size_type __pos) const noexcept
258 __glibcxx_assert(__pos < this->_M_len);
259 return *(this->_M_str + __pos);
263 constexpr const_reference
264 at(size_type __pos) const
267 __throw_out_of_range_fmt(__N("basic_string_view::at: __pos "
268 "(which is %zu) >= this->size() "
269 "(which is %zu)"), __pos, this->size());
270 return *(this->_M_str + __pos);
274 constexpr const_reference
275 front() const noexcept
277 __glibcxx_assert(this->_M_len > 0);
278 return *this->_M_str;
282 constexpr const_reference
283 back() const noexcept
285 __glibcxx_assert(this->_M_len > 0);
286 return *(this->_M_str + this->_M_len - 1);
290 constexpr const_pointer
291 data() const noexcept
292 { return this->_M_str; }
294 // [string.view.modifiers], modifiers:
297 remove_prefix(size_type __n) noexcept
299 __glibcxx_assert(this->_M_len >= __n);
305 remove_suffix(size_type __n) noexcept
307 __glibcxx_assert(this->_M_len >= __n);
312 swap(basic_string_view& __sv) noexcept
319 // [string.view.ops], string operations:
323 copy(_CharT* __str, size_type __n, size_type __pos = 0) const
325 __glibcxx_requires_string_len(__str, __n);
326 __pos = std::__sv_check(size(), __pos, "basic_string_view::copy");
327 const size_type __rlen = std::min<size_t>(__n, _M_len - __pos);
328 // _GLIBCXX_RESOLVE_LIB_DEFECTS
329 // 2777. basic_string_view::copy should use char_traits::copy
330 traits_type::copy(__str, data() + __pos, __rlen);
335 constexpr basic_string_view
336 substr(size_type __pos = 0, size_type __n = npos) const noexcept(false)
338 __pos = std::__sv_check(size(), __pos, "basic_string_view::substr");
339 const size_type __rlen = std::min<size_t>(__n, _M_len - __pos);
340 return basic_string_view{_M_str + __pos, __rlen};
345 compare(basic_string_view __str) const noexcept
347 const size_type __rlen = std::min(this->_M_len, __str._M_len);
348 int __ret = traits_type::compare(this->_M_str, __str._M_str, __rlen);
350 __ret = _S_compare(this->_M_len, __str._M_len);
356 compare(size_type __pos1, size_type __n1, basic_string_view __str) const
357 { return this->substr(__pos1, __n1).compare(__str); }
361 compare(size_type __pos1, size_type __n1,
362 basic_string_view __str, size_type __pos2, size_type __n2) const
364 return this->substr(__pos1, __n1).compare(__str.substr(__pos2, __n2));
367 [[nodiscard, __gnu__::__nonnull__]]
369 compare(const _CharT* __str) const noexcept
370 { return this->compare(basic_string_view{__str}); }
372 [[nodiscard, __gnu__::__nonnull__]]
374 compare(size_type __pos1, size_type __n1, const _CharT* __str) const
375 { return this->substr(__pos1, __n1).compare(basic_string_view{__str}); }
379 compare(size_type __pos1, size_type __n1,
380 const _CharT* __str, size_type __n2) const noexcept(false)
382 return this->substr(__pos1, __n1)
383 .compare(basic_string_view(__str, __n2));
386#ifdef __cpp_lib_starts_ends_with // C++ >= 20
389 starts_with(basic_string_view __x) const noexcept
391 return _M_len >= __x._M_len
392 && traits_type::compare(_M_str, __x._M_str, __x._M_len) == 0;
397 starts_with(_CharT __x) const noexcept
398 { return !this->empty() && traits_type::eq(this->front(), __x); }
400 [[nodiscard, __gnu__::__nonnull__]]
402 starts_with(const _CharT* __x) const noexcept
403 { return this->starts_with(basic_string_view(__x)); }
407 ends_with(basic_string_view __x) const noexcept
409 const auto __len = this->size();
410 const auto __xlen = __x.size();
411 return __len >= __xlen
412 && traits_type::compare(end() - __xlen, __x.data(), __xlen) == 0;
417 ends_with(_CharT __x) const noexcept
418 { return !this->empty() && traits_type::eq(this->back(), __x); }
420 [[nodiscard, __gnu__::__nonnull__]]
422 ends_with(const _CharT* __x) const noexcept
423 { return this->ends_with(basic_string_view(__x)); }
424#endif // __cpp_lib_starts_ends_with
426#if __cplusplus > 202002L
427#if _GLIBCXX_HOSTED && !defined(__cpp_lib_string_contains)
428 // This FTM is not freestanding as it also implies matching <string>
429 // support, and <string> is omitted from the freestanding subset.
430# error "libstdc++ bug: string_contains not defined when it should be"
434 contains(basic_string_view __x) const noexcept
435 { return this->find(__x) != npos; }
439 contains(_CharT __x) const noexcept
440 { return this->find(__x) != npos; }
442 [[nodiscard, __gnu__::__nonnull__]]
444 contains(const _CharT* __x) const noexcept
445 { return this->find(__x) != npos; }
448 // [string.view.find], searching
452 find(basic_string_view __str, size_type __pos = 0) const noexcept
453 { return this->find(__str._M_str, __pos, __str._M_len); }
457 find(_CharT __c, size_type __pos = 0) const noexcept;
461 find(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
463 [[nodiscard, __gnu__::__nonnull__]]
465 find(const _CharT* __str, size_type __pos = 0) const noexcept
466 { return this->find(__str, __pos, traits_type::length(__str)); }
470 rfind(basic_string_view __str, size_type __pos = npos) const noexcept
471 { return this->rfind(__str._M_str, __pos, __str._M_len); }
475 rfind(_CharT __c, size_type __pos = npos) const noexcept;
479 rfind(const _CharT* __str, size_type __pos, size_type __n) const noexcept;
481 [[nodiscard, __gnu__::__nonnull__]]
483 rfind(const _CharT* __str, size_type __pos = npos) const noexcept
484 { return this->rfind(__str, __pos, traits_type::length(__str)); }
488 find_first_of(basic_string_view __str, size_type __pos = 0) const noexcept
489 { return this->find_first_of(__str._M_str, __pos, __str._M_len); }
493 find_first_of(_CharT __c, size_type __pos = 0) const noexcept
494 { return this->find(__c, __pos); }
498 find_first_of(const _CharT* __str, size_type __pos,
499 size_type __n) const noexcept;
501 [[nodiscard, __gnu__::__nonnull__]]
503 find_first_of(const _CharT* __str, size_type __pos = 0) const noexcept
504 { return this->find_first_of(__str, __pos, traits_type::length(__str)); }
508 find_last_of(basic_string_view __str,
509 size_type __pos = npos) const noexcept
510 { return this->find_last_of(__str._M_str, __pos, __str._M_len); }
514 find_last_of(_CharT __c, size_type __pos=npos) const noexcept
515 { return this->rfind(__c, __pos); }
519 find_last_of(const _CharT* __str, size_type __pos,
520 size_type __n) const noexcept;
522 [[nodiscard, __gnu__::__nonnull__]]
524 find_last_of(const _CharT* __str, size_type __pos = npos) const noexcept
525 { return this->find_last_of(__str, __pos, traits_type::length(__str)); }
529 find_first_not_of(basic_string_view __str,
530 size_type __pos = 0) const noexcept
531 { return this->find_first_not_of(__str._M_str, __pos, __str._M_len); }
535 find_first_not_of(_CharT __c, size_type __pos = 0) const noexcept;
539 find_first_not_of(const _CharT* __str,
540 size_type __pos, size_type __n) const noexcept;
542 [[nodiscard, __gnu__::__nonnull__]]
544 find_first_not_of(const _CharT* __str, size_type __pos = 0) const noexcept
546 return this->find_first_not_of(__str, __pos,
547 traits_type::length(__str));
552 find_last_not_of(basic_string_view __str,
553 size_type __pos = npos) const noexcept
554 { return this->find_last_not_of(__str._M_str, __pos, __str._M_len); }
558 find_last_not_of(_CharT __c, size_type __pos = npos) const noexcept;
562 find_last_not_of(const _CharT* __str,
563 size_type __pos, size_type __n) const noexcept;
565 [[nodiscard, __gnu__::__nonnull__]]
567 find_last_not_of(const _CharT* __str,
568 size_type __pos = npos) const noexcept
570 return this->find_last_not_of(__str, __pos,
571 traits_type::length(__str));
577 _S_compare(size_type __n1, size_type __n2) noexcept
579 using __limits = __gnu_cxx::__int_traits<int>;
580 const difference_type __diff = __n1 - __n2;
581 if (__diff > __limits::__max)
582 return __limits::__max;
583 if (__diff < __limits::__min)
584 return __limits::__min;
585 return static_cast<int>(__diff);
589 const _CharT* _M_str;
592#if __cplusplus > 201703L && __cpp_lib_concepts && __cpp_deduction_guides
593 template<contiguous_iterator _It, sized_sentinel_for<_It> _End>
594 basic_string_view(_It, _End) -> basic_string_view<iter_value_t<_It>>;
596#if __cplusplus > 202002L
597 template<ranges::contiguous_range _Range>
598 basic_string_view(_Range&&)
599 -> basic_string_view<ranges::range_value_t<_Range>>;
603 // [string.view.comparison], non-member basic_string_view comparison function
605 // Several of these functions use type_identity_t to create a non-deduced
606 // context, so that only one argument participates in template argument
607 // deduction and the other argument gets implicitly converted to the deduced
610#if __cpp_lib_three_way_comparison
611 template<typename _CharT, typename _Traits>
614 operator==(basic_string_view<_CharT, _Traits> __x,
615 type_identity_t<basic_string_view<_CharT, _Traits>> __y)
617 { return __x.size() == __y.size() && __x.compare(__y) == 0; }
619 template<typename _CharT, typename _Traits>
622 operator<=>(basic_string_view<_CharT, _Traits> __x,
623 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
625 -> decltype(__detail::__char_traits_cmp_cat<_Traits>(0))
626 { return __detail::__char_traits_cmp_cat<_Traits>(__x.compare(__y)); }
628 template<typename _CharT, typename _Traits>
631 operator==(basic_string_view<_CharT, _Traits> __x,
632 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
634 { return __x.size() == __y.size() && __x.compare(__y) == 0; }
636 template<typename _CharT, typename _Traits>
639 operator==(basic_string_view<_CharT, _Traits> __x,
640 basic_string_view<_CharT, _Traits> __y) noexcept
641 { return __x.size() == __y.size() && __x.compare(__y) == 0; }
643 template<typename _CharT, typename _Traits>
646 operator==(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
647 basic_string_view<_CharT, _Traits> __y) noexcept
648 { return __x.size() == __y.size() && __x.compare(__y) == 0; }
650 template<typename _CharT, typename _Traits>
653 operator!=(basic_string_view<_CharT, _Traits> __x,
654 basic_string_view<_CharT, _Traits> __y) noexcept
655 { return !(__x == __y); }
657 template<typename _CharT, typename _Traits>
660 operator!=(basic_string_view<_CharT, _Traits> __x,
661 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
663 { return !(__x == __y); }
665 template<typename _CharT, typename _Traits>
668 operator!=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
669 basic_string_view<_CharT, _Traits> __y) noexcept
670 { return !(__x == __y); }
672 template<typename _CharT, typename _Traits>
675 operator< (basic_string_view<_CharT, _Traits> __x,
676 basic_string_view<_CharT, _Traits> __y) noexcept
677 { return __x.compare(__y) < 0; }
679 template<typename _CharT, typename _Traits>
682 operator< (basic_string_view<_CharT, _Traits> __x,
683 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
685 { return __x.compare(__y) < 0; }
687 template<typename _CharT, typename _Traits>
690 operator< (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
691 basic_string_view<_CharT, _Traits> __y) noexcept
692 { return __x.compare(__y) < 0; }
694 template<typename _CharT, typename _Traits>
697 operator> (basic_string_view<_CharT, _Traits> __x,
698 basic_string_view<_CharT, _Traits> __y) noexcept
699 { return __x.compare(__y) > 0; }
701 template<typename _CharT, typename _Traits>
704 operator> (basic_string_view<_CharT, _Traits> __x,
705 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
707 { return __x.compare(__y) > 0; }
709 template<typename _CharT, typename _Traits>
712 operator> (__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
713 basic_string_view<_CharT, _Traits> __y) noexcept
714 { return __x.compare(__y) > 0; }
716 template<typename _CharT, typename _Traits>
719 operator<=(basic_string_view<_CharT, _Traits> __x,
720 basic_string_view<_CharT, _Traits> __y) noexcept
721 { return __x.compare(__y) <= 0; }
723 template<typename _CharT, typename _Traits>
726 operator<=(basic_string_view<_CharT, _Traits> __x,
727 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
729 { return __x.compare(__y) <= 0; }
731 template<typename _CharT, typename _Traits>
734 operator<=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
735 basic_string_view<_CharT, _Traits> __y) noexcept
736 { return __x.compare(__y) <= 0; }
738 template<typename _CharT, typename _Traits>
741 operator>=(basic_string_view<_CharT, _Traits> __x,
742 basic_string_view<_CharT, _Traits> __y) noexcept
743 { return __x.compare(__y) >= 0; }
745 template<typename _CharT, typename _Traits>
748 operator>=(basic_string_view<_CharT, _Traits> __x,
749 __type_identity_t<basic_string_view<_CharT, _Traits>> __y)
751 { return __x.compare(__y) >= 0; }
753 template<typename _CharT, typename _Traits>
756 operator>=(__type_identity_t<basic_string_view<_CharT, _Traits>> __x,
757 basic_string_view<_CharT, _Traits> __y) noexcept
758 { return __x.compare(__y) >= 0; }
759#endif // three-way comparison
762 // [string.view.io], Inserters and extractors
763 template<typename _CharT, typename _Traits>
764 inline basic_ostream<_CharT, _Traits>&
765 operator<<(basic_ostream<_CharT, _Traits>& __os,
766 basic_string_view<_CharT,_Traits> __str)
767 { return __ostream_insert(__os, __str.data(), __str.size()); }
770 // basic_string_view typedef names
772 using string_view = basic_string_view<char>;
773 using wstring_view = basic_string_view<wchar_t>;
774#ifdef _GLIBCXX_USE_CHAR8_T
775 using u8string_view = basic_string_view<char8_t>;
777 using u16string_view = basic_string_view<char16_t>;
778 using u32string_view = basic_string_view<char32_t>;
780 // [string.view.hash], hash support:
782 template<typename _Tp>
786 struct hash<string_view>
787 : public __hash_base<size_t, string_view>
791 operator()(const string_view& __str) const noexcept
792 { return std::_Hash_impl::hash(__str.data(), __str.length()); }
796 struct __is_fast_hash<hash<string_view>> : std::false_type
800 struct hash<wstring_view>
801 : public __hash_base<size_t, wstring_view>
805 operator()(const wstring_view& __s) const noexcept
806 { return std::_Hash_impl::hash(__s.data(),
807 __s.length() * sizeof(wchar_t)); }
811 struct __is_fast_hash<hash<wstring_view>> : std::false_type
814#ifdef _GLIBCXX_USE_CHAR8_T
816 struct hash<u8string_view>
817 : public __hash_base<size_t, u8string_view>
821 operator()(const u8string_view& __str) const noexcept
822 { return std::_Hash_impl::hash(__str.data(), __str.length()); }
826 struct __is_fast_hash<hash<u8string_view>> : std::false_type
831 struct hash<u16string_view>
832 : public __hash_base<size_t, u16string_view>
836 operator()(const u16string_view& __s) const noexcept
837 { return std::_Hash_impl::hash(__s.data(),
838 __s.length() * sizeof(char16_t)); }
842 struct __is_fast_hash<hash<u16string_view>> : std::false_type
846 struct hash<u32string_view>
847 : public __hash_base<size_t, u32string_view>
851 operator()(const u32string_view& __s) const noexcept
852 { return std::_Hash_impl::hash(__s.data(),
853 __s.length() * sizeof(char32_t)); }
857 struct __is_fast_hash<hash<u32string_view>> : std::false_type
860 inline namespace literals
862 inline namespace string_view_literals
864#pragma GCC diagnostic push
865#pragma GCC diagnostic ignored "-Wliteral-suffix"
866 inline constexpr basic_string_view<char>
867 operator""sv(const char* __str, size_t __len) noexcept
868 { return basic_string_view<char>{__str, __len}; }
870 inline constexpr basic_string_view<wchar_t>
871 operator""sv(const wchar_t* __str, size_t __len) noexcept
872 { return basic_string_view<wchar_t>{__str, __len}; }
874#ifdef _GLIBCXX_USE_CHAR8_T
875 inline constexpr basic_string_view<char8_t>
876 operator""sv(const char8_t* __str, size_t __len) noexcept
877 { return basic_string_view<char8_t>{__str, __len}; }
880 inline constexpr basic_string_view<char16_t>
881 operator""sv(const char16_t* __str, size_t __len) noexcept
882 { return basic_string_view<char16_t>{__str, __len}; }
884 inline constexpr basic_string_view<char32_t>
885 operator""sv(const char32_t* __str, size_t __len) noexcept
886 { return basic_string_view<char32_t>{__str, __len}; }
888#pragma GCC diagnostic pop
889 } // namespace string_literals
890 } // namespace literals
892#if __cpp_lib_concepts
895 // Opt-in to borrowed_range concept
896 template<typename _CharT, typename _Traits>
897 inline constexpr bool
898 enable_borrowed_range<basic_string_view<_CharT, _Traits>> = true;
900 // Opt-in to view concept
901 template<typename _CharT, typename _Traits>
902 inline constexpr bool
903 enable_view<basic_string_view<_CharT, _Traits>> = true;
906_GLIBCXX_END_NAMESPACE_VERSION
909#include <bits/string_view.tcc>
911#endif // __cplusplus <= 201402L
913#endif // _GLIBCXX_EXPERIMENTAL_STRING_VIEW